Cardiac support device and method

ABSTRACT

The invention relates to a cardiopulmonary bypass pump that can be used with medication to put the heart into asystole or near asystolic status. This gives the physician enough time to perform diagnostic and/or therapeutic procedures and also allows the diseased heart to recover from ischemic insults without additional hemodynamic stress, and also facilitates certain cardiac procedures. 
     The patent describes equipment used in conjunction with medication to temporarily replace the function of the heart and to allow the heart to survive with minimal oxygen supply for hours or days, and for the heart to recover from ischemic or other insult or other damage without being subjected to a heavy working load. The invention provides a means to stop blood flow to the heart for a relatively long period of time, thereby allowing the performance of certain procedures that require coronary artery blockade. It also allows the heart to stop contracting, which may result in safer and easier performance of some procedures. 
     A pump is used to drain blood from the patient&#39;s veins into a gas exchanger. The exchanger oxygenates the blood and removes carbon dioxide from the blood, then the pump pumps the blood back into the patient. The device maintains blood pressure at a preset level in a pulsatile fashion. A medication is given to the patient while the device is in use in order to stop the heart or slow the heart rate to a minimal level to decrease cardiac oxygen requirements without significant hemostasis in the pulmonary circulation. 
     The systemic circulation can be supported entirely by the pump with the heart in asystole. This allows enough time for certain diagnostic and therapeutic procedures to be performed. The device may also allow the diseased heart to recover from an ischemic insult. The system receives feedback from arterial pressure sensors and utilizes this data to maintain the arterial pressure at a preset level by adjusting the pump activity. There is an electrocardiogram (EKG) gating mechanism that coordinates the pump activity with contraction of the heart to avoid active contraction of the heart against the pulsatile pressure head of the device pump. There is an interaction between pressure control and EKG gating to ensure that the arterial pressure is maintained at a preset level and to avoid the heart contracting against the pump.

BACKGROUND

It is well known that if the blood supply to the heart is significantlycompromised and the demand of the heart for blood supply remainsunchanged or increases (so called supply demand mismatch), the muscle ofthe heart will be irreversibly damaged in a few minutes to a few hours,depending on the severity of the mismatch and other factors. This timelimit of the survival of the heart in this condition—only minutes tohours—presents a major challenge to physicians and exposes patients tohigh mortality and morbidity during myocardial infarction (heartattack). Patients may not be able to survive the heart attack or, ifthey do, they may develop severe heart failure due to extensive injuryto the heart. This imposes a huge social and financial burden onsociety.

In most situations, blood supply to the heart can not be improvedimmediately and, if the demand of the heart for blood supply can bedecreased significantly, the heart may survive this insult much longerpending further treatment and may gain enough time to recover from theinsult. This is conventionally accomplished in part by keeping thepatient at rest, including the use of sedatives if necessary. Also, thepatient is typically given supplemental oxygen to make enhanced use ofthe available cardiovascular function.

The heart works as a pump to maintain blood circulation. The function ofcirculation is to maintain blood pressure at a certain level to provideperfusion to the organs of the body. All the prior art inventionsavailable to artificially support circulation are designed as leftventricular supportive devices with an assumption that the heart willcontinue to play a central role in maintaining blood circulation. Theyare designed to assist the heart when it can not work normally such as aleft ventricular assistant device. Alternatively, the prior art devicesare intended to replace the heart's function without consideringcoordination between the heart and the system, such as thecardiac-pulmonary bypass machine, which also requires a complicatedprocedure.

Previous inventions were designed to provide cardiac-pulmonary bypass asan assistance to the heart and allow the heart to work continuously eventhere is significant compromise of blood supply to the heart, or toreplace the function of the heart when it fails to function. Forexample, U.S. Pat. No. 4,540,399 to Litzie discloses a cardiopulmonarybypass machine. It allows a physician to control the speed of the pumpto maintain blood pressure at a certain level. U.S. Pat. No. 5,879,316to Safar also discloses a cardiopulmonary bypass machine, which providesdifferential perfusion of different organs including the heart. Itconsiders selective perfusion of the heart as a part of resuscitationand allows the heart to stop for one to two hours. However, it requiresa complicated procedure.

A design of a pump was made public (Tokano H. et. al, World J. Surgery9:78-88, 1985), which has EKG gating and left arterial pressure feedback to control work load on the heart. The left arterial pressure isused to determine the work load on the heart and, therefore, to controlpump activity for unloading volume from the left ventricle. It is also aleft ventricular assistant device and allows the heart to continue tocontract and to assume a central role in circulation.

A number of inventions have disclosed cardiopulmonary bypass machinesfor open-heart surgery. They require insertions of a catheter into theheart chambers and the great blood vessels surgically and extensivetechnical support.

SUMMARY OF THE INVENTION

If a machine can maintain blood pressure, a physician can put the heartinto asystole, or near asystole, without significant compromise to thefunction of the organs. Patients can survive without the heart'sfunctioning, and the heart survives until a definitive treatment takesplace. The heart has enough time to recover from a transient myocardialinsult.

The invention relates to a cardiac support system which can be used inconjunction with medication to render the heart in an asystolic ornearly asystolic status. It is a goal of the invention that the workload of the heart is minimized by coordination between the activities ofthe heart and of the system during induction and maintenance of theasystolic or nearly asystolic status and later the resumption of thenormal activity of the heart.

Because the invention allows a physician to put an acutely diseasedheart into an asystolic or nearly asystolic status, the physician hasenough time to perform further diagnostic tests and therapeuticintervention, and to transfer the patient to a referral center forfurther treatment. The invention is designed with the concept that theheart needs to stop working if its blood supply is significantlycompromised. It is also a consideration of the invention that the pumpsystem disclosed herein is easy to use by most medical practitioners inmost medical facilities throughout the world.

No previous invention has been designed with the concept ofintentionally rendering the heart temporarily asystolic or nearly so inorder to allow adequate time for the performance of diagnostic tests,therapeutic maneuvers, and recovery from the myocardial insult. Toachieve this goal, the device and the heart need precisely coordinatedactivity. This may be achieved by a complex interaction between theelectromechanical activity of the heart and the device. None of theprior art devices teaches adequate mechanisms for coordination betweenthe heart and pump activity. It is important to have mechanisms ofcoordination between the cardiopulmonary pump and the heart whenattempting purposeful induction and maintenance of an asystolic ornearly asystolic status.

For example, '399 does not take it into account that the heart needs tostop working. Neither '399 nor '316 teach intentional cessation of theheart as a primary treatment instead of as a resuscitation attempt or asa part of open heart surgery. Neither patent has a mechanism tosufficiently coordinate the contraction of the heart with the activityof the cardiopulmonary bypass machine, such as EKG gated pump activitywith interaction between pressure control and EKG gating, although someof them did have EKG gated activity and pressure feedback. Althoughthere are EKG gating and pressure control (only left atrial pressurefeed back) devices known in the art, there is no interaction among EKG,arterial pressure, contraction of the heart and pump activity.

The invention provides a method of facilitating cardiac rest in a humancomprising induction of a controlled asystolic state in the human andapplication of life support techniques while the human is in theasystolic state.

Typically, the induction includes administration of a medication ormedications such as calcium channel blockers, beta adrengenic blockers,antiarrhythmics and potassium. These drugs are well known in the art.Examples of calcium channel blockers include verapamil and diltiazem.Examples of beta adrenergic blockers (or beta adrenergic receptorantagonists) include propranolol, esmolol and bretylium. Examples ofantiarrhythmic agents include lidocaine, adenosine, procainamide andquinidine.

Some of the medications can be placed in more than one category. Forinstance, the beta blockers can be useful as antiarrhythmic agents. Ifpotassium is used to slow or to stop the heart, intravenous potassiumchloride is a preferred embodiment. For this purpose, the potassium isadministered in a large vein or a central vein, such as the femoral,jugular or subclavian vein. Other drugs may be administered as is wellknown in the art. For example, pain killers and sedatives may beindicated. Examples include morphine, phenobarbital and diazepam.

Life support techniques of the invention include application of a closedextra-corporeal circulation system. Such a system typically includes avenous conduit, a gas exchanger, a pump for pumping at least a portionof the patient's blood, and an arterial conduit. Preferably, theartificial circulation system is arranged such that the venous conduitis connected to a vein of the patient, the arterial conduit is connectedto an artery of the patient, the gas exchanger is connected to at leastone of the venous conduit and the arterial conduit, and the pump isconnected to at least one of the venous conduit and the arterialconduit. Usually the gas exchanger is adapted both to remove at least aportion of a quantity of carbon dioxide from the patient's blood and toadd a quantity of oxygen to the patient's blood. A heat exchanger may beincluded, and it is connected with any two of the group comprising thearterial conduit, the pump, the gas exchanger, and the venous conduit.Preferably, the pump included in the circulation system is a pulsatilepump.

The closed system preferably includes an EKG gating mechanism that hasan EKG sensor means for sensing the human's heartbeat, and a feedbackmeans for coordinating the EKG sensor means with the pump wherein thepump discontinues for a time of at least one heartbeat sensed by the EKGsensor means and resumes pumping when the heartbeat is not sensed by theEKG sensor means at a rate or at a volume which is needed to maintainblood pressure above a preset level and is controlled by an intrinsicrate or volume setting.

The closed system may include an arterial pressure sensor that has afeedback means for coordinating the arterial pressure of the human withthe pumping of the pump such that the pump changes at least one ofpumping rate and pumping volume when the pressure sensor senses apressure different from a predetermined arterial pressure range. Thepressure sensor is also used to re-initiate the pump activity after EKGgating means stops the pumping activity as described herein and when theblood pressure sensor senses a fall in blood pressure.

The pump increases a volume output of the pump by changing at least oneof pump rate and pump volume when the pressure sensor senses an arterialpressure less than the predetermined arterial pressure and decreases apumping rate when the pressure sensor senses an arterial pressure higherthan the predetermined arterial pressure.

The closed system includes a gating coordination means for coordinatingthe EKG sensor means with the arterial pressure sensor means. To promoteadequate arterial blood pressure in the human, the pressure sensor meansis adapted to override the EKG gating means to control the pump for atleast one of pumping rate and pumping volume.

The pump preferably includes at least two chambers. The two chamberedpump is coordinated such that one of the chambers is receiving bloodinto itself while the other of the chambers is emptying blood fromitself. The closed system further includes a QRS reset mechanism that isadapted to sense a QRS complex generated by the patient and to reset thepump's pumping when the QRS complex is sensed by the reset mechanism. Inthis embodiment, the resetting of the pumping is accomplished such thatthe chamber that was receiving blood before the reset will resumereceiving blood until a predetermined volume is received, and such thatthe chamber emptying blood will resume emptying blood until apredetermined volume is emptied.

The invention further provides a method of facilitating cardiac rest ina patient comprising induction of a state of either reversiblebradycardia or reversible asystole in conjunction with the applicationof life support techniques. Bradycardia can refer to a heart rate offrom 1 to 60 beats per minute. Alternatively, bradycardia can refer to aheart rate of from 1 to 10 beats per minute.

Additionally, the invention provides a method of facilitating cardiacrest in a patient who has sustained a cardiac insult comprisinginduction of a controlled state of lowered metabolism of the myocardiumof the human. This state includes decreased heart rate and decreasedoxygen utilization. During this time, life support techniques areadministrated including extra-corporeal circulation through a closedsystem. The closed system has a pump, a gas exchanger, a heat exchanger,and a systolic gating mechanism. The controlled state of loweredmetabolism facilitates further treatment to the heart without injury tothe heart or compromise of blood supply the other vital organs.

The gas exchanger is typically adapted to remove C02 from and to add 02to at least a portion of a volume of blood pumped through the closedsystem. Also, the gas exchanger is usually located in series between avein of the human and the pump.

Preferably, the systolic gating mechanism is adapted to coordinate thepump and systole such that the pump is restrained from pumping duringsystole. The gating mechanism preferably includes a pressure sensor anda feedback means to the pump. The feedback means is adapted to controlat least one of pumping rate and cardiac volume output. Typically, atleast one of the pumping rate and the volume output is sufficient tomaintain a predetermined pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an embodiment of the pump system.

FIG. 2 is a sectional view of the pumping chambers of a preferredembodiment.

FIG. 3 is a view of a pump of the invention.

DETAILED DESCRIPTION OF INVENTION

The system includes a pump which drains the blood from the veins andpumps the blood back to the arteries of a patient. Typically the patientis a human, but the invention encompasses veterinary applications also.There is preferably a gas exchanger between the arteries and the pump,which oxygenates the blood and removes carbon dioxide from the blood.Typically there is heat exchanger, which keeps the blood at atemperature close to normal body temperature. Preferably, the heatexchanger is integrated with either the gas exchanger or the pumpingchamber. This decreases the possibility of formation of air bubbles,since the solubility of gas changes when temperature changes.

There are preferably one way valves between the pump and veins orarteries, which allow the blood to flow only from the veins to the pumpand from the pump to the arteries. Furthermore, there is usually amechanism or mechanisms to control circulation volume through the pumpas needed.

Additionally, there is usually a mechanism for coordinating the pumpingactivity with heart contraction if heart contraction occurs or wheneverthis coordination is needed. Arterial pressure or EKG information may beused for this coordinating purpose. For example, a pressure sensor maybe integrated into the arterial catheter, which delivers blood to theartery, or a separate arterial pressure sensor may be used to measurearterial pressure. This pressure signal feeds back to the pump forcontrolling the rate of the pump for maintaining the arterial pressureat a preset level.

The QRS complex of the EKG and arterial pressure from the patient can beused to coordinate pump activity with contraction of the heart. There ispreferably coordination between the EKG gating and pressure control ofthe pump activity. The QRS complex stops the pump, and a fall inarterial pressure detected by the pressure control system of the pumpresumes the pump activity. This design assures that the heart does notcontract against the pump and that pump activity starts right after theheart completes its contraction. In this manner, the pump will work incoordination with the heart to avoid stress from the pump workingagainst the heart and to facilitate induction and maintenance of theasystolic or nearly asystolic status and resumption of the normalactivity of the heart when desired.

If arterial pressure is below a preset value, the pressure control willoverride the EKG gating to assure adequate perfusion pressure to theorgans. During asystolic or nearly asystolic status, the pump iscontrolled by an intrinsic pumping rate or volume to maintain bloodpressure within a present range. EKG gating and the pressure controlmechanism continue to work to avoid the heart contracting against thepump. Appropriate pressure ranges are well known in the art. The presetpressure is selected to maintain adequate perfusion to the vital organs.For example, a mean arterial pressure of about 60 to 90 mm Mercury isusually thought to be appropriate.

A pressure sensor can also be used to measure central venous pressure.If central venous pressure is too high, such as higher than 18 mmHg, thepump rate or the pumping volume or both is increased for draining thevenous blood and, therefore, decreases the central venous pressure to anoptimal level, such as 12 mmHg. This may be particularly important whenmyocardial infarction involves the right ventricle. In this situation,an increase in central venous pressure may cause increased pressure ofthe right ventricle. This increases oxygen consumption of the rightventricle and decreases blood supply to the right ventricle and,therefore, can cause further damage to the right ventricle or prevent orcompromise the recovery of the cardiac muscle from the insult. Thiscentral venous pressure control means works in conjunction with anarterial pressure control and an EKG gating means and preferably workswhen the arterial pressure control and EKG gating are fully operational.

In a preferred embodiment, the pump includes two pumping chambers thatare mechanically compressible and extendible. These two chambers work ina coordinated manner, meaning that while one is filling, the other isdraining. This double chamber design provides an advantage in that thepump pumps the blood into the artery and drains the blood from the veinwhenever the pump is reset by a QRS complex. For example, when a QRScomplex resets the pump with one chamber in the pumping status and theother in draining status, the pump will restart with the pumping chamberpumping and draining chamber draining.

Alternatively, the pump can be adapted to sense which chamber containsmore blood volume, and reset itself such that a chamber with more bloodis in a pumping status and the other is in a draining status. Withoutthis design, when a single chamber is reset by a QRS complex at the endof its pumping status, it will be less able to pump blood into theartery and, therefore, will be less able to maintain the blood pressureeffectively. This is even more important when the heart rate isrelatively fast. A single chamber pump would not have enough time tocoordinate with spontaneous heart contractions, which would result inineffective pump activity and decrease in blood pressure. It would causehypoperfusion of the organs including the heart and brain. Damage to theorgan could occur.

This preferred design more effectively maintains arterial pressure andunloads the right ventricle and, therefore, the left ventricle since, ifthe right ventricle is loaded, it will pump the blood to the leftventricle in a following cardiac cycle. This preferred design alsoallows a relatively long pumping and draining cycle of each chamberwithout compromise of blood circulation since the two chambers work in acoordinated fashion.

In a preferred embodiment, the pumping phase of each chamber is shorterthan the draining phase with the gas exchanger located between the veinand the chambers. This generates a pulsatile pressure to mimicphysiological blood pressure, which is important to enhance perfusion tothe heart and other organs. It allows a relatively longer time for bloodto flow through the gas exchanger at lower speed. This permits betteroxygenation with a smaller exchanger and less sheering force. This inturn makes it possible to decrease blood volume circulating in thepumping system and cause less hemolysis and less coagulation abnormalitydue to less sheering force.

The chambers are connected to the venous and arterial catheters. Thechamber volume is adjustable as needed. For example, when heart rate isfaster, chamber volume may decrease with an increase in the pumpingrate. Both the venous and arterial catheters contain one-way valves,which only allow blood to flow from the vein to the pump and from thepump to artery. When a chamber is expanded, a negative pressure iscreated in the chamber, which draws blood from the vein. When a chamberis compressed, a positive pressure is created which pumps the blood intothe artery through the arterial catheter. These actions create apulsatile pressure, which can avoid side effects of non-pulsatilepressure on the perfusion of the organs of the human body. It is knownthat non-pulsatile pressure may be harmful to the organs.

Selection of pump rates and chamber volumes are well within the skill ofthe ordinary practitioner of the invention. Pump rate is usuallyselected from a range of about 30 to 100 contractions per minute. Morepreferably, the range is from 50 to 85 beats per minute. Thepractitioner is aware of the inter-relationship between pump rate andpump volume. For instance, a faster pump rate would be expected tocorrelate with a somewhat lower chamber volume, whereas a larger chambervolume would be expected to accommodate a somewhat lower pump rate.Usually, in an adult patient, the chamber would contain about 60 to 100milliliters of blood volume. Pediatricians are well aware of thedifferent volume and pressure requirements for their patients, and wouldadjust the parameters accordingly.

The venous draining catheter preferably enters the chamber from the topof the chamber to allow possible air bubbles to accumulate in a coneshaped top space where they can be readily removed. The arterialcatheter is typically located at bottom of the chamber to decrease thepossibility of air bubbles entering the arterial system, which may causeair embolism. The coordination between the two chambers can bedisengaged when necessary to stop one pump for any reason, such as toremove air bubbles accumulated in the chamber. This coordination can bere-engaged as well. Typically the chamber contains priming solution forfilling up the system and purging air bubbles to establishcardiopulmonary bypass circulation, such as normal saline.

The following additional preferred embodiments refer to the figures forillustrative purposes. FIG. 1 is a diagram of the pump system. Number 2is a catheter which drains blood from the vein of a patient to a pumpand contains a one way valve only allowing the blood to flow from thepatient to the pump. Number 4 is a pump which creates a negativepressure to drain blood from the vein and positive pressure to pump theblood through a gas exchanger and back to the artery of the patient.Number 6 is a catheter which connects the pump to the gas exchanger or aheat exchanger or both (8) and then to the body of the patient. Theblood from the vein is pumped back to the artery of the patient throughthis catheter which also contains a pressure sensor (9), which senses anarterial pressure of the patient and feeds back this information to thepump to maintain a preset arterial pressure. Number 8 is a commerciallyavailable gas and heat exchanger combination, which removes carbondioxide and oxygenates the blood and keeps the temperature of the bloodat similar level to the body temperature of the patient. Number 10 is anEKG unit located in the pump or connected to the pump and is used togate the pump activity. It may stop the pump if an EKG signal, such as aQRS complex, is sensed. It may be bypassed on the choice of a physicianor over-ridden by a pressure control function of the pump.

FIG. 2 is a sectional view of the pumping chambers. Number 12 is a solidand non-expandable portion of a pumping chamber. Number 14 is a solidand non-expandable portion of a pumping chamber, which is equivalent infunction and similar to the chamber numbered 12. Air can accumulate inthe top portion of the cone shaped space for removal. Number 16 is anexpandable portion of the pumping chambers. When it is expanded, anegative pressure is created in the chamber and blood is drained intothe chamber. When it is compressed, a positive pressure in the chamberpumps the blood into the artery of the patient through a gas exchanger.Number 18 is an expandable portion of the other pumping chamberequivalent to that described as number 16. Number 20 and 22 arestopcocks for each corresponding chamber for removing air bubblesaccumulated in the chambers. Numbers 24 and 26 are solid cylinders toprotect each corresponding pumping chamber. Numbers 28 and 30 are solidrods connecting a driving mechanism to the bottom portion of therespective pumping chambers for compressing and expanding the chambers.Numbers 32 and 34 are solid bottom portions of the pumping chambers.Numbers 36 and 38 are solid cone shaped top portions of eachcorresponding pumping chamber. Numbers 42, 44 and 46 are tubingsconnecting the gas exchanger to the pumping chambers and containing oneway valves, which allow the blood to flow only from the gas exchanger tothe pumping chambers. Number 21 is a gas exchanger, which is used tooxygenate the blood and to remove carbon dioxide from the blood. Number48 is an inlet receiving the blood from a patient. Number 50 is a baseof the pump, which contains pump machinery and control mechanisms.

FIG. 3 is a drawing of the pump. Numbers 60 and 62 are two equivalentpumping chambers. Number 64 is a gas exchanger. Number 66 is a tubingdraining the blood from a patient to the gas exchanger. Number 68 istubing for delivering blood from the pumping chambers to the patient.Numbers 72 and 70 are tubings which connect the corresponding pumpingchamber to number 68. Each tubing contains a one way valve allowingblood to flow only from the corresponding pumping chamber to thepatient, or from the patient to the appropriate chamber. Number 74 is acontinuation of the tubing numbered as 72. Number 76 is the base of thepump. Number 78 is a screen showing EKG and blood pressure tracings.Numbers 80, 82, 84 and 86 are switches for control of the pump, such asEKG gating and pressure control engagement and disengagement of the twopumping chambers.

EXAMPLE

When a patient needing cardiac rest or cardiopulmonary circulation isidentified, venous and arterial catheters are inserted with standardprocedure in a major vein and artery, such as the femoral vein andartery or the jugular vein and/or axillary arteries. The venous andarterial catheters are connected to the cardiopulmonary bypass machine.After reliable bypass circulation is established, medication, such asesmolol (a beta adrenergic blocker) or diltiazem (a calcium channelblocker) or both, if needed, are infused into patient's vein in anincremental manner to allow the heart rate to gradually decrease over ashort period of time such as 15 minutes.

If control of the heart rate is not adequate, potassium may be used tocreate a hyperkalemic status and a severe bradycardia or asystolicstatus. When ventricular tachycardia or fibrillation occurs, large dosesof antiarrhythmics, such as Quinidine and Procainaminde, may be used tostop these rhythm disturbances without the usual consequences ofasystole caused by the medication. These medications can be used toinduce asystolic or nearly asystolic status.

The bypass machine is activated when the arterial pressure is below apre-set level, such as 60 mm Hg mean arterial pressure. The EKG gatingand pressure control mechanisms are activated and functions in thepreviously described manner to avoid the heart contracting against themachine. Eventually, heart rate decreases to a few beat per minutes.Hemostasis in the pulmonary circulation is avoided by letting the heartcontract a few times per minute. Pump rate or pumping volume or both arecontrolled by pressure feedback from the artery to maintain the bloodpressure at a preset level. The patient's blood circulation may bemaintained in this manner for hours to days depending on the clinicalcondition of the patient.

When the patient is ready to be weaned off the machine, infusion of themedication is decreased in a decremental manner with the pump operatingunder pressure control and EKG gating mechanisms. This maintainsadequate perfusion of the organs and avoids the heart contractingagainst pressure generated by the pump. This also allows a cardiologistto perform procedures such as angioplasty and coronary stenting to theleft main coronary artery or to severely stenotic coronary arteries orboth.

The heart may be put into asystole for a period of time to allow certainprocedures to be performed such as minimally invasive bypass surgery orsome catheter based intervention, such as angioplasty and stenting tothe coronary arteries. Previously, such patients were thought to beunsuitable or at extremely high risk for angioplasty and required bypasssurgery, since failure of angioplasty to open these vessels presents animmediate risk for massive heart attack or death. With the pumpreplacing the function of the heart and the heart in an asystolicstatus, angioplasty and stenting or minimal bypass surgery to thesevessels can be done and the result can be monitored with minimal risk ofmassive heart attack or death if the procedure fails, since the functionof the heart is replaced by the pump and the work load on the heart isextremely low.

The pump is also can be used for respiratory failure, which will providereliable oxygenation of the blood and avoid intubation of the trachea.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated by reference into thespecification to the same extent as if each individual publication,patent or patent application was specifically and individually indicatedto be incorporated herein by reference.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationscan be practiced within the scope of the appended claims.

I claim:
 1. A method of facilitating cardiac rest in a patient who hassustained a cardiac insult comprising: (a) induction of a controlledstate of lowered metabolism of the myocardium of the human, said stateincluding decreased heart rate and decreased oxygen utilization, and (b)administration of life support techniques including extra-corporealcirculation through a closed system, said system having a pump, a gasexchanger, a heat exchanger, and a systolic gating mechanism, whereinsaid controlled state of lowered metabolism facilitates furthertreatment to the heart without injury to the heart or compromise ofblood supply the other vital organs; wherein said systolic gatingmechanism is adapted to coordinate the pump and systole such that thepump is restrained from pumping during systole.
 2. The method of claim 1wherein said gating mechanism includes a pressure sensor and a feedbackmeans to the pump, said feedback means adapted to control at least oneof (a) pumping rate and (b) cardiac volume output, wherein at least oneof the pumping rate and the volume output is sufficient to maintain apredetermined pressure.
 3. A closed extra-corporeal circulation systemto support the blood circulation of a human, said system comprising: avenous conduit; a gas exchanger; a pump for pumping at least a portionof the human's blood, said pump having at least two chambers and being apulsitile pump; an arterial conduit; an EKG gating mechanism; anarterial pressure sensor; and a QRS reset mechanism, wherein saidcirculation system is arranged such that the venous conduit is connectedto a vein of the patient, the arterial conduit is connected to an arteryof the patient, the gas exchanger is connected to at least one of thevenous conduit and the arterial conduit, and the pump is connected to atleast one of the venous conduit and the arterial conduit, wherein thegas exchanger is adapted to remove at least a portion of a quantity ofcarbon dioxide from the patient's blood and is further adapted to add aquantity of oxygen to the patient's blood, wherein the gating mechanismincludes: (a) an EKG sensor means for sensing the human's heartbeat, and(b) a feedback means for coordinating the EKG sensor means with the pumpwherein the pump discontinues for a time of at least one heartbeatsensed by the EKG sensor means and resumes pumping when the heartbeat isnot sensed by the EKG sensor means at a rate or a volume sufficient tomaintain blood pressure above a preset level and controlled by anintrinsic rate or volume setting, wherein the arterial pressure sensorincludes a feedback means for coordinating the arterial pressure of thehuman with the pumping of the pump such that the pump changes at leastone of pumping rate and pumping volume when the pressure sensor senses apressure different from a preset arterial pressure level, and furtherwherein the pressure sensor is adapted to re-initiate the pumping afterthe EKG gating means stops the pumping activity or when the bloodpressure sensor senses a fall in blood pressure below the preset level,wherein the pump increases a volume output of the pump by changing atleast one of pump rate and pump volume when the pressure sensor sensesan arterial pressure less than the predetermined arterial pressure anddecreases a pumping rate when the pressure sensor senses an arterialpressure higher than the predetermined arterial pressure, wherein theclosed system further includes a gating coordination means forcoordinating the EKG sensor means with the arterial pressure sensormeans, wherein the pressure sensor means is adapted to override the EKGgating means to control the pump for at least one of pumping rate andpumping volume, the QRS reset mechanism adapted to (a) sense a QRScomplex generated by the patient and to (b) reset the pump's pumpingwhen the QRS complex is sensed by the reset mechanism, wherein theresetting of the pumping is accomplished such that the chamber that wasreceiving blood before the reset will resume receiving blood until apredetermined volume is received, and such that the chamber emptyingblood will resume emptying blood until a predetermined volume isemptied, wherein said system further includes a heat exchanger connectedwith any two of the group comprising the arterial conduit, the pump, thegas exchanger, and the venous conduit.
 4. A method of facilitatingcardiac rest in a human comprising: (a) induction of controlledasystolic state in the human, and (b) application of life supporttechniques while the human is in the asystolic state, wherein theapplication of life support techniques includes application of a closedextra-corporeal circulation system having: (c) a venous conduit, (d) agas exchanger, (e) a pump for pumping at least a portion of the human'sblood, and (f) an arterial conduit, said circulation system arrangedsuch that the venous conduit is connected to a vein of the patient, thearterial conduit is connected to an artery of the patient, the gasexchanger is connected to at least one of the venous conduit and thearterial conduit, and the pump is connected to at least one of thevenous conduit and the arterial conduit, wherein the gas exchanger isadapted to remove at least a portion of a quantity of carbon dioxidefrom the patient's blood and is further adapted to add a quantity ofoxygen to the patient's blood, wherein the closed system includes an EKGgating mechanism, said gating mechanism having: (g) an EKG sensor meansfor sensing the human's heartbeat, and (h) a feedback means forcoordinating the EKG sensor means with the pump wherein the pumpdiscontinues for a time of at least one heartbeat sensed by the EKGsensor means and resumes pumping when the heartbeat is not sensed by theEKG sensor means, wherein said pumping provides a rate or a volumesufficient to maintain blood pressure above a preset level and iscontrolled by an intrinsic rate and/or volume setting.
 5. The method ofclaim 4 wherein the closed system includes an arterial pressure sensor,said pressure sensor having a feedback means for coordinating thearterial pressure of the human with the pumping of the pump such thatthe pump changes at least one of pumping rate and pumping volume whenthe pressure sensor senses a pressure different from a predeterminedarterial pressure range, and wherein the pressure sensor re-initiatesthe pumping after EKG gating means stops the pumping activity and whenthe blood pressure sensor senses a fall in blood pressure below thepreset level.
 6. A method of claim 5 wherein the pump increases a volumeoutput of the pump by changing at least one of pump rate and pump volumewhen the pressure sensor senses an arterial pressure less than thepreset arterial pressure level and decreases a pumping rate when thepressure sensor senses an arterial pressure higher than the presetarterial pressure level.
 7. The method of claim 5 wherein the closedsystem includes a gating coordination means for coordinating the EKGsensor means with the arterial pressure sensor means.
 8. The method ofclaim 7 to promote adequate arterial blood pressure in the human whereinthe pressure sensor means is adapted to override the EKG gating means tocontrol the pump for at least one of pumping rate and pumping volume. 9.The method of claim 6 wherein the pump includes at least two chambers.10. The method of claim 9 wherein a two chambered pump is coordinatedsuch that one of the chambers is receiving blood into itself while theother of the chambers is emptying blood from itself.
 11. The method ofclaim 10 wherein the closed system further includes a QRS resetmechanism, said mechanism adapted to (a) sense a QRS complex generatedby the patient and to (b) reset the pump's pumping when the QRS complexis sensed by the reset mechanism, wherein the resetting of the pumpingis accomplished such that the chamber that was receiving blood beforethe reset will resume receiving blood until a predetermined volume isreceived, and such that the chamber emptying blood will resume emptyingblood until a predetermined volume is emptied.